Alcohol dehydrogenase

Zinc-containing NAD oxyreductase which, in the presence of NAD, reversibly catalyses primary and secondary alcohols to the corresponding aldehydes or ketones and also the back reaction of these (aldehyde to alcohol).

Occurs in bacteria, yeasts, plants, in the liver and in the retina of the eye. Alcohol dehydrogenases are found in all living organisms.

In the liver, alcohol dehydrogenase (among other mechanisms, see also "Microsomal ethanol-oxidizing system") converts blood alcohol into acetaldehyde. This reaction is used to determine the blood alcohol level. In the retina, the enzyme serves to reduce the vitamin A aldehyde (all-trans-retinal) to retinol.

In human metabolism there are 5 different alcohol dehydrogenases. All are dimers of two polypeptide chains, each subunit containing two zinc ions (Zn2+). One of these ions is essential for the function of the enzyme.

A competitive inhibitor of alcohol dehydrogenase is fomepizole (4-methylpyrazole), which is available as an antidote for acute intoxication with ethylene glycol and methanol.

1. Ammon H et al (2014). Hunnius Pharmaceutical Dictionary. Walter de Gruyter GmbH Berlin/Boston S 59